Gymnastatins I-K, cancer cell growth inhibitors from a sponge-derived Gymnascella dankaliensis

The Halichondria sponge-derived fungus, Gymnascella dankaliensis, was cultured in a malt extract medium containing the bromine source. Three new metabolites, gymnastatins I (5)-K (7), have been isolated from the mycelial MeOH extract. The spectroscopic analyses using 1D and 2D NMR techniques have established the stereostructures of 5-7 in which chlorine atoms in gymnastatins A (1)-C (3) are respectively replaced by bromine atoms. All of the isolated metabolites (5-7) exhibited growth inhibition against the P388 cancer cell line. Furthermore, gymnastatins I (5) and J (6) showed appreciable growth inhibition against the human cancer cell lines.